The increase in integration degree and storage capacity of semiconductor memory devices raises the fail occurrence possibility of semiconductor cells during a manufacturing process. This serves as a factor that reduces yield. In general, when a semiconductor memory device has several failed memory cells or even one failed memory cell, the semiconductor memory device may not be placed on the market as a product.
In order to improve the yield of high integration semiconductor memory devices, a variety of attempts have been made. A representative example is a repair technology using a fuse.
In a semiconductor memory device, a repair technology used for repairing a failed cell to allow a chip to operate normally is generally divided into two methods. A first method is a fuse cutting method using a laser device. A second method is a method in which a predetermined amount of high current is applied to a substance forming a fuse so that the substance of the fuse is ruptured and as a result the state of the fuse is electrically shorted.
In particular, since the second method may be used even after the assembly of a chip into a package is completed, it is referred to as an antifuse method. Since a failed cell in a package state may be repaired into a normal cell using the antifuse method, the antifuse method is gaining popularity from chip manufacturers when compared to the fuse cutting method using the laser device.
However, in the antifuse method, problems arise when the fuse substance is not completely ruptured through in one rupturing operation, a misoperation is likely to be caused, and a reliability issue may be raised because the fuse is likely to return to a state before rupture.